Many people suffering from Adult-onset Macular Degeneration (AMD) have damage to the Macula that has repositioned the Fovea (center of the Macula) causing a new visual-axis to be slightly offset from the original (normal) visual-axis. This is very common in older people. The result, in many cases, is Diplopia. Double vision occurs when the image that one eye sees does not coincide with the image that the other eye sees when looking with both eyes at the same time at the same physical object, making it appear that there are two of everything in the field of view of the Macula and Fovea. The brain can accommodate for slight differences, but, when the offset becomes too great for the brain to accommodate-double vision results. Peripheral vision is not affected by AMD.
Many AMD patients still have relatively good acuity in the AMD eye but the offset of the visual-axis still results in double vision. For patients with AMD in both eyes, the result most likely will be double vision. Another cause of double vision is Strabismus of which there are several types and which sometimes is a result of the right and left eye muscles' inability to coordinate to focus in on an object and make the two images fuse. Double vision sufferers have to find their own method of coping with the problem. For some people, surgery is the answer. For the other people, one way to cope is to close one eye while viewing. This quickly becomes tiring. Another method is to wear an eye-patch instead of closing the eye. The eye-patch interferes with eyeglasses making that option also unsatisfactory. A problem with both methods is that the person loses the peripheral vision in that eye. Losing peripheral vision can actually be dangerous if the person is in a dangerous industrial setting, or driving a vehicle where it is important to see danger approaching with the periphery of one's vision. One crude method of addressing the problem has been the use of Prism Bars held in front of one eye by Ophthalmologists to guess at the amount of induced prism required in eyeglass lenses by the patient to bring the two images together as one. That method is not accurate and has been the source of much dissatisfaction on the part of patients as well as the Ophthalmologists. There are also hand held rotary prisms available. Here again hand held means not very accurate.
Thus, there has always been a need for a more accurate and satisfactory way of improving the seeing ability of such individuals.